1. Field of the Invention
The invention is directed to power semiconductor modules and, more particularly, to power semiconductor modules having a contact spring providing pressure contact to ensure electrical connection of the elements thereof.
2. Description of the Related Art
Know power semiconductor modules of the type described herein are described, example from German Published Patent Application DE 197 19 703 A1. Power semiconductor modules of this type comprise, according to the prior art, a housing with at least one electrically insulating substrate arranged therein, preferably for direct mounting on a cooling component. The substrate, for its part, comprises a body made up of an insulating material with a plurality of mutually insulated metallic connecting tracks situated thereon and power semiconductor components which are situated on the connecting tracks and connected to the connecting tracks in a circuit-conforming manner. Furthermore, such known power semiconductor modules have external connection elements for external load and auxiliary connections and also internal connecting elements. These internal connecting elements for circuit-conforming connections in the power semiconductor module are usually embodied as wire bonding connections.
Likewise known are pressure-contact-connected power semiconductor modules, such as are shown in German Published Patent Application DE 42 37 632 A1. In modules such as discussed in that document, the pressure device has a stable, preferably metallic, pressure element for building up pressure, an elastic cushion element for storing pressure, and a bridge element for introducing pressure onto separate regions of the substrate surface. The bridge element is preferably configured as a plastic molding having a surface which faces the cushion element and from which a multiplicity of pressure fingers extend towards the substrate surface.
By means of a pressure device of this type, the substrate is pressed onto a cooling component and the heat transfer between the substrate and the cooling component is thus established permanently and reliably. In this case, the elastic cushion element maintains constant pressure conditions under different thermal loads and over the entire life cycle of the power semiconductor module.
German Published Patent Application DE 10 2004 025 609 A1 discloses a power semiconductor module comprising a baseplate and auxiliary connection elements embodied as contact springs. In accordance with this document, a cover applies pressure to the contact springs for reliable electrical contact-connection. In this case, the contact springs are arranged in a mount in the housing, although the mount is not shown or described in detail.
German Published Patent Application DE 10 2006 006 421 A1 discloses a power semiconductor module having at least one connection element embodied as a contact spring. The module comprises a first contact device, a resilient section and a second contact device. In this case, a first plastic molding has a shaft arranged perpendicular to the substrate for receiving a connection element. The shaft has, for its part, a lateral cutout for the rotationally secure arrangement of the connection element and a recess for an assigned partial body of a second plastic molding, wherein the partial body likewise has a lateral cutout and, on the side remote from the substrate, a cutout through which the first contact device of the connection element extends.
German Published Patent Application DE 10 2006 058 692 A1 likewise discloses a power semiconductor module with contact springs having an S-shaped deformation in the region of the lower contact device. In accordance with this document, the deformation serves to afford protection against the contact spring falling out. The deformation of the contact spring is positioned between the substrate and the cutouts of the housing.
German Published Patent Application DE 10 2005 024 900 A1 likewise discloses a contact spring secured against falling out. In accordance with this document, the contact spring is held in the housing by the lower turns of the spring, which have a larger diameter than the upper turns of the spring, and thus ensures protection against the spring falling out of the housing.
What is disadvantageous about the prior art here is a technologically dictated excessively large projection of the auxiliary contact spring beyond the housing in the unmounted state and without arrangement of the control circuit board. The pressure contact spring projects beyond the housing at most by its entire spring excursion, which increases the risk of damage in the form of deformation of the spring head, that is to say of the upper contact device of the auxiliary connection. The spring impact area or the contact area on the mountable control circuit board has to be made large enough to ensure, under all circumstances, a reliable electrical contact-connection of the power semiconductor module to the mountable control circuit board.